Method of and apparatus for cleaning and surface-coating glass and the like



g 28, 1945' w. MORGAN 7 2,383,470 7 METHOD OF AND APPARATUS FOR CLEANAND SUR FACE-COATING GL AND THE E ed Aug. 1944 3 Sheets-Sheet l Fil IN VEN TOR.

Willard L.Morgan. WW WLL Y ATTORNEYS 3 Shees-Sheet 2 L. MORGAN FiledAug. 14, 1944 W v IIQVENTOR. iHar LMorgan. m r .3 'W

' AT TORNEYS SURFACE-COATING GLASS AND THE LIKE Aug. 28,. 1945.

Aug. 28, 1945.

W. L. MORGAN METHOD OF AND APPARATUS FOR CLEANING AND SURFACE-COATINGGLASS AND THE LIKE 3 Sheets-Sheet 3 Filed Aug. 14, 1944 a mu mn M n: .bV 00 4 w a? l r a 2 av m "\Am D S 0 {m E 1 I p M .1 n m F "KM o o o o oo o m 5 O O O O O O O o o o o o o o o o o o o o o v o o o o o o o a I mw s mm r -m IIIIIIIIIIIIIIII l4 IIIIIIIIII I! INIYENTOR.

WIHQr'd L.Morg0n. 3% W ATTORNEYS Patented Aug. 28, 1 945 I 2,383,7lt'

ME'rnon or AND APPARATUS FOR CLEAN- mG AND sunrises-comma GLASS AND'rnELIKn Willard L. Morgan,

Columbus, Ohio, assignor to Libbey-Owens-Ford Glass Company, Toledo,

Ohio, a corporation of Ohio Application August 14, 1944, Serial No.549,402

(on. 117-s v Claims. This invention relates to a method of and apparatusfor cleaning and surface-coating glass P and the like. Moreparticularly, the present invention relates directly to a method ofcleaning glass, porcelain, siliceous compositions, metals, or Othersupport material to a surface or surfaces of which there is to vbeapplied a coating, such, for

example, as a low reflection coating, or a metallized or reflectivelayer of a suitable material for the production of various articles,such as mirrors, reflectors, and the like. I

It is frequently desirable and necessary to clean glass and metallicsurface extremely thoroughly. This is especially true when the glass,metallic, or the like support surface is to be coated subsequently witha coating or a reflective layer, by means of thermal evaporation orsputtering withtors and similar optical articles or objects. It has longbeen recognized that if the support surface to be coated in suchoperations is not thoroughly clean and free of all foreign "particles orcontaminants, the reflective layer deposited by the coating, operationswill not adheresatisfactorily to the surface. Although some degree ofadherence may besecured upon a surface which is only partially clean,the resulting coated surface will not be uniform, but will exhibitareasof poor adhesion which may appear as hazy areas, streaks, anduncoated pinholes. Such areas of poor adhesion, if numerous enough willinterfere with the reflective value of the finished article, and inaddition these may function as potential centers of corrosion.

Conventional methods of cleaning glass or metalli surfaces which are tobe employed as supports formetallic reflecting layers involve, commonly,a preliminary chemical cleaning of the surface to be coated, such as bywashing with a solution of a mineral acid containing sodium dichromate,or by scrubbing with a dilute solution in a vacuum, to thereby producemirrors, reflecl molecules of the air; that intense bombardment of thesurface to be cleaned results therefrom; and that the force of thisbombardment is suflicient to effect the physical removal of thecontaminants, such as particles of foreign matter, adhering to thesurface undergoing treatment. Despite extensive investigation of widevariations of the various operating conditions and techniques involvedin such procedures, these conventional methods are not, however,satisfactory. On the contrary, they most frequently result inimperfectly cleaned surfaces which, as above stated are not satisfactoryfor the production of metallically coated reflecting articles of thedesired or optium quality, particularly with reference to freedom frompinholes, adherence and corrosion resistance.

It is, th'ereforaone of the objects of the present invention to providean improved method of cleaning glass, metallic, or other surfaces withthe utmost thoroughness.

It has also been recognized that if cleaned surfaces, such as thosecleaned in the conventional manner as described above, are to be coatedwith a metallic reflecting layer, or with oth'er coatings, withanydegree of success whatsoever, it is imperative that such coatingoperations be undertake'nimmediately after the conclusion of cleaningoperations. If the operation of coating the cleaned surface is notimmediately effected, the cleaning operations, such as those described,must necessarily be repeated, since foreign particles in the atmosphere,if from no oth'er source, will at once contaminate the surface to becoated despite all precautions, however elaborate. The wasteful,time-consuming, and otherwise uneconomical consequences of repeatedcleanings are readily apparent, as are the operational difliculties andscheduling problems involved in conducting the of an alkali containing,if desired, a mild abrasive.-

all traces of the cleaning reagent. The preliminarily cleaned surfacemay then be further subjected to the effects of a high voltageelectricaldischarge, generally in air under a vacuum of, for

example, 0.01 millimeter of mercury. Such electrical dischargetreatments are based on the theory that the electrical glow dischargeimparts greatly increased translational velocity to the coatingoperations immediately after completing the cleaning operations. Evenwhere the cleaned articles are immediately transferred to acoating'chamber the momentary contact with the atmosphere is suiflcientto cause contamination of the support by greases and lint and to causeconsiderable spoilage.

It is, therefore, another object of my invention to provide an improvedmethod of protecting cleaned glass, metallic, or the like supportingsurfaces until such time as it is desired to perform the depositionoperations on such cleaned surfaces for the production of metallizedarticles, mirrors, and low reflection articles of a coated nature.

Heretofore, it has not been possible, with conventional preliminarychemical cleaning and washing operations or technique, to thoroughlycleanse articles or objects formed from glass, metal, or other materialsexcept possibly those having flat, plane, or sheet-like smooth surfaces.It was impossible, with such methods, to thoroughly clean articles orobjects which were multi-sided, or of irregular contour, or of unevensurface or surfaces such, for example, as tumblers, jars, vases, toys,lenses, prisms, buttons, and the like.

It is, therefore, another object of my present invention to provide animproved method of cleaning glass, metallic, or other surfaces with theutmost degree of thoroughness, whatever the dimensional, or angular, orother irregularities may be; and, when such surfaces are to be coatedwith a metallic reflective layer or other coating, to provide animproved method of protecting the cleaned surfaces from contaminationuntil such time as it is desired to undertake deposition operationsthereupon.

It is a further object of this invention to provide an improved methodof cleaning glass, metallic, or other surfaces of whatever physicalconfiguration. with the utmost degree of thoroughness, and to provide animproved method of protecting such cleaned surfaces from contaminationuntil such time as it is desired to undertake metallic coatin ordeposition operations thereupon; it being another object of my inventionto perform both of said operations or methods automatically andcontinuously preferably by immediately successive steps.

Other objects and advantages of my invention will be apparent from thefollowing detailed description and examples hereinafter set forth, and

from the appended claims and drawings forming a part of thisspecification, in which drawings like reference characters designatecorrespond'ng parts in the several views.

In said drawings:

Fig. 1 is an elevational view, partly broken away of a soiled article ofmanufacture to be treated by the method and apparatus of the presentinvention.

Fig. 2 is a view similar to Fig. 1 showing the article after it has beenmechanically'and chemically cleaned, showing some of the foreign matteror particles still remaining on the surface thereof.

Fig. 3 is an elevational view, partly broken away,

of the article of the preceding views and illustrating diagrammatically,one mode, means, or method of subjecting the surface or surfaces of thearticle to flame contact to remove all foreign matter or particlestherefrom.

Fig. 4 is a View similar to Figs. 1 and 2 and showing the thoroughlycleansed article having its surface or surfaces saturated with aprotective coating, such as glycol vapors, or the like, to prevent thelodgment of any foreign matter thereupon.

Fig. 5 is a View similar to Fig. 4 and showing the article with itsprotective surface coating ready to be placed in storage.

Fig. 5a is an elevational view, on a reduced scale,

showing the article of the preceding views after,

the temporary protective film has been removed and a final or permanentreflective coating or layer has been deposited thereupon.

Fig. 6 is a side elevational View, partly in section and somewhatdiagrammatic, illustrating a suitable apparatus embodying the presentinvention, ior thoroughly cleaning articles by fiame contact to burn offforeign matter or particles and for subjecting the cleaned articles to asaturation treatment by vapors from some suitable organic liquid orliquids, such as glycol, or the like.

Fig. '7 is a side elevational view, partly in section and somewhatdiagrammatic, of another form of apparatus embodying the invention forperforming or carrying out the steps performed by the apparatus of Fig.6.

Fig. 8 is a front elevational view, on an enlarged scale, takensubstantially along the line 8-8 of Fig. 6, looking in the direction ofthe arrows.

Fig. 9 is an enlarged detail fragmentary plan view of the burnerarrangement of Figs. 6, 7 and partly in elevation, of another form ofapparatus embodying the present invention for applying a suitable finalor permanent coating or film to thoroughly cleaned articles such, forexample, as bolts.

Fig. 12 is a perspective view of one of the articles treated in theapparatus of Fig. 11; and

Fig. 13 is a schematic view illustrating the different parts or units ofthe apparatus of my invention and which may be employed for carrying outthe several steps of the method or process of said invention.

Before explaining in detail the present invention it is to be understoodthat the invention is not limited in its application to the details ofconstruction and arrangement of parts illustrated in the accompanyingdrawings, since the invention is capable of other embodiments and ofbeing practised or carried out in various ways. It is to be understoodalso that the phraseology or terminology employed herein is for thepurpose of description and not of limitation, and it is not intended tolimit the invention herein claimed beyond the requirements of the priorart.

7 Generally speaking, my invention has to do with a method or processand a suitable apparatus for performing or carrying out the same, whichis adapted particularly for the thorough cleaning of surfaces formedfrom support material of various kinds such, for example, as glass, andarticles of manufacture and the like which may be formed from varioussiliceous or vitreous materials, or the like. It has to do further withthe protection, during storage, of these thoroughly cleaned surfaces andprior to the application thereto of a permanent coating or surfacefinish which may be, for example, a high or low reflective coating orlayer formed from metal, or other materials. Moreover, the method orprocess and the apparatus of my invention are particularly well adaptedfor the thorough cleaning of the surfaces of articles whether suchsurfaces be irregular or uneven, curved, or plane surfaces.

In accordance with my present invention, the surface to be thoroughlycleaned is, preferably, first mechanically and chemically cleaned andthereafter subjected to a thorough cleaning by treatment of the surfaceor surfaces directly with a flame from a gas burner, or series ofburners of any desired type. The direct surface momentary contactburning serves to completely remove all foreign material and particlesfrom the surface and to leave said surface in an absolutely clean state.In order to preserve the cleanliness of the surface, I next subject saidcleaned surface to the vapors of some suitable organic liquid to producethereupon a protective film or coating before the article is placed instorage where it may remain for an indefinite period of time withoutdanger of contamination, to be later provided with a suitable permanentcoating.

This permanent coating may be applied in various ways. For examplathearticle or surface to be coated may be subjected to a glow discharge inan enclosed chamber and the prelimlnarily or protective organic liquidfilm orcoating removed therefrom by bombardment. Preferably, immediatelythereafter and while in the same chamber, the clean surface or articlemay be provided with the desired coating by the thermal evaporation ofsome suitable material, or by other means.

' pletely clean, the effect of drawing glass over surfaces.

If desired,.the protective coati g may be removed from the surface orarticle in any desired manner and by any suitable means, such as by theapplication of suitable heating or by evaporation in a high vacuum, anda final and permanent coating applied thereto while located within achamber or compartment in which a suitable material is evaporated andapplied to the thoroughly cleaned surface. By way of example, thislast-mentioned coating may be produced in an electrically heated oven orfurnace,

or in a similarly heated tunnel within which is located a crucible, orseries of crucibles containing the material, such as metal, to providethe final coating. The crucibles are heated either electrically or inany'other suitable manner to a temperature which is sufficiently high toeffect the evaporation of and dispelling or dispersing of molecules ofthe metal, or other material, which will be deposited upon the surfaceor article, or plurality ofsuch, which are located within the tunnel.

In accordance with one form of my invention the steps of thoroughlycleaning the article by its subjection to direct contact with a flame orflames to completely free the article of all foreign. matterandcontaminants and the application of a final permanent film or layer ofthe desired coating material to the cleaned article, may follow in rapidsuccession.

I have discovered that glass, porcelain, various siliceous, metallic, orthe like surfaces of the types hereinabove described, preferablypreliminarily cleaned by conventional means, may

be cleaned thoroughly and completely by subjection for a relativelyshort period of time to the relatively high temperature action of a gasflame, or the like. The fact of the absolute cleanness of suchflame-treated surfaces may be established or proven in a number ofconventional ways. Thus, for example, if a fine, clean fiber or whiskerof glass is drawn across the surface of a piece of glass which has beencleaned by rubbing with ordinary detergents, the fiber or whisker movesfreely over the surface. When, however, a fiber or whisker is drawnacross a glass surface which has been cleaned according to the methodand apparatus of my present invention, it will seize, and rasp. Thisaction of the fiber is brought about by the friction between the glasssurfaces. Such friction is not appreciable unless the glass surfaces arecomglass is reduced to that of the low frictional forces exhibited bythe contaminants.

Another test for determining the complete cleanliness of surfacescleaned in accordance with the method and apparatus of my invention, isthe production on the surfaces of so-called breath figures. For example,it is well known that moisture condenses unevenly and in dropletformation upon incompletely cleaned glass surfaces, such as thosecleaned by conventional methods. 0n the contrar when a glass surfacewhich has been cleaned in the manner herein described is breathed upon,a condensation apparently black in color results upon the surface. Thedark coloration is due to the extreme uniformity, continuous nature, andthinness of the moisture film condensed in this way, and ischaracteristic only of extremely clean Further, if ametallic surface iscleaned in action of a metallic vapor such, for example, as mercuryvapor, no change in appearance of the surface is observed, although itis known that metallic deposition has occurred thereon. 0n

the other hand, when metallic surfaces cleaned according to conventionalpractise are exposed to mercury vapors, a marked area whereon vaporcondensation and mercury deposition has occurred, is at once readilyobservable. This phenomenon is closely related to, and in fact com monlyidentified as, a breath figure effect.

I have discovered further that glass, metallic,

or the like surfaces of the types hereinabove described, when cleaned inaccordance with the method of thepresent invention, exhibit extreme- 11y desirable properties with respect to providing an optimum surface forthe subsequent deposition of metallic or other material layers bythermal evaporation or'sputtering. Reflecting layers deposited onsurfaces cleaned in this way demonstrate excellent uniform adherence tothe support material. In addition, they are of uniform color andreflecting or other optical values and practically without uncoatedpinhole areas.

I have made the further discovery that surfaces cleaned ln accordancewith th method of my invention may be effectively maintained in aconditionof absolute cleanliness by depositing thereon a film or layerof an organic liquid which is not substantially subject tovolatilization under the conditions of temperature at which the surfaceis to be protected from contamination during transfer to the coatingoperation or storage prior to such operation.

, The widespread industrial functions of my invention, as well as theeconomic simplifications permitted thereby, are at once apparent, sinceit enables more effective cleaning of glass, metallic, and the likesupport surfaces than has heretofore been possible, and also permits theprotection of such cleaned surfaces to thereby satisfy a long felt buthitherto incompletely fulfilled industrial necessity. In addition, itsdiversified utility is greatly enhanced since my invention is obviouslyequally applicable and well adapted to the thorough cleaning of planeand irregular surfaces, and to the absolute protection fromcontamination of any and all such cleaned sin'faces.

One preferred sequence of operations or steps comprising my inventionmay be as follows, although I wish it to be distinctly understood thatthis sequence is outlined merely for purposes of illustration and that,if desired, such steps of the method in certain instances as, forexample, preliminary mechanical or chemical cleaning and/or storage, maybe omitted entirely:

1. Preliminary mechanical or chemical cleaning of the surface orsurfaces.

2. Heat treatment.

3. Deposition of organic liquid film on the cleaned surface.

4. Storage of protected articles.

5. Removal of protective film.

6. Deposition of metallic or outer coating material layer.

Referring now to th drawings and particularly to Figs. 1 to 5,inclusive, thereof, I have shown in these figures one kind or type ofarticle whose surface 'or surfaces are thoroughly cleaned and thenprotected against the accumulation of foreign matter, particles, orcontaminants, in accordance with the method or process and apparatusembodying my invention.

Figs. 1 to 5, inclusive, are intended to illustrate an article and alsothe steps of preliminarily cleaning the surface thereof mechanically andchemically; thoroughly cleaning the preliminarily cleaned surface bydirect contact of the surface with a hot flame or flames from a suitableburner or burners; and thereafter the application to the thoroughlycleaned surface, of a protective coating or film which may be providedby the vaporization of some suitable organic liquid and the condensationof the vapors onto the surface.

The article shown in Figs. 1 to 5, inclusive, has the general appearanceof a hob-nail type of vase or jar. The article may be formed from glass,siliceous material, pottery, metal, or the like. As shown, the vase orjar is represented as a whole at IS. The outer face or surface of thewalls is provided with a plurality of humps or bump-like projectingportions 15a, thus presenting an outer rough or uneven surface for thearticle.

In Fig. 1 the article is shown inits so-called original state with alayer or encrustation of dirt or other foreign matter or particles,indicated at IS. The article is preferably preliminarily cleanedmechanically and chemically in any con ventional manner, as by scrubbingor rubbing the surface with some suitable aqueous solution to remove themajor portion of the contaminating substances from said surface.

The second step of the method or process of cleaning the articlecomprises the subjection of the partially cleaned article, that is theouter surface thereof upon which remain particles or greasy coatings llof foreign matter (see Fig. 2) to momentary direct contact with hotflames from a gas burner or burners of any desired type. As seen in Fig.3 the burner or burners are provided with nozzles l8 which emit hotflames iila. which directly contact or impinge the surface to be cleanedand completely spread over the entire area of said surface to blanketthe same with flame, somewhat in the manner illustrated diagrammaticallyin this figure. In practise, a series or succession of the articles lmay be passed between spaced rows of burner nozzles, the flames fromwhich impinge all portions of the exterior surfaces of said articles. Ifdesired, the articles may be carried upon a suitable conveyer in a pathextending between the burners.

Moreover, if desired, the articles may be caused the skin or outer layerthereof and thus the flame or flames will have no deleterious effectupon the article. Since the body of each of the articles is considerablycooler than their outer skins or surfaces, the cooling effect of thebody will work outwardly toward the skin to cool the latter reasonablypromptly. It is to be understood that the flames thoroughly clean notonly the relatively flat or plane surfaces of the article l5, but alsothoroughly clean the uneven surfaces provided by the projections orbumps 15a.

As the third step in practising my method and after all foreign matterandcontaminants have been completely removed from the surface of thearticle, said article is passed, preferably on a suitable conveyer, intoa heated chammr to which there is admitted the vapors from some suitableheated Or boiling organic liquid. If desired, I may admit anon-combustible mixture of the organic liquid vapors with carbon dioxideand nitrogen to the chamber. The vapors are indicated generally at IS inFig. 4. As these vapors contact the relatively cooler outer surface ofthe article, which is cooler than the heated vapors they condensethereon and form a protective layer or film-like coating, shown at 20 inFig. 5. It will be understood that this protective fllm or coating 20prevents any possibility of the contamination of the outer surface orskin of the cleansed article. If desired, the film-protected articlesmay be placed in storage in readiness to have suitable permanent coatinglayers applied thereto at some future time.

Moreover, and as will be explained more fully below, the cleansed andsurface-protected article l5 of Fig. 5 may be removed from storage andplaced in a suitable vacuum chamber such, for example, as that shown inFig. 9. While in said chamber the article I5 is first subjected to aglow discharge and bombardment to remove the protective surface coating20 and thereafter, while remaining in the same chamber, has applied tothe surface or surfaces thereof, a final or permanent coating of somesuitable nature which, if desired, may be placed thereupon by depositionresulting from the thermal evaporation of some suitable material such,for example, as metal. One such suitable chamber for removing theprotective coating or film 20 and for applying the final and permanentcoating, is illustrated in Fig. 9, mentioned above, and which will befully discussed hereinafter.

Application of heat to the surface-protected article It of Fig. 5, afterplacing the article in the vacuum chamber, by means of electricallyheated wire or wires W may also be employed to cause a rapidvaporization in the high vacuum of the protective organic liquid filmand after such removal within the apparatus of Fig. 10, a permanentdeposit of metallic nature, reflective qualities, or low reflectionproperties of a suitable nature may be then coated upon the freshlyexposed thoroughly cleaned surfaces of the article by thermalevaporation, or by sputtering of suitable materials.

A finished article with its final or permanent coating is shown in Fig.5a, the article as a whole being shown at A and its final reflective orother coating at B.

In accordance with the present invention, cleaning operations upon theglass, siliceous, or metallic surface are preliminarily conducted in aconventional manner, that is to say, by mechanical means to remove thesuperficial dirt Hi from the article. ll! of Fig. 1 to present thearticle of Fig. 2 upon the surface of which small particles II of dirtremain after the conventional cleaning.

As hereinabove described, such mechanical cleaning may comprise simplyrubbing with brushes or cloths containing soapy water; or it may involvewashing with asolution of a mineral acid, such, for example, as nitricacid, or sulfuric acid containing sodium dichromate. Alternatively, itmay involve scrubbing with a dilute solution of an alkali containing amild abrasive. Preferably, although not necessarily, preliminarymechanical cleaning is effected by soaking or scrubbing the surfaces orarticles in a warm detergent solution, preferably containing a wettingagent such, for example, as trisodium phosphate in amount, say, 5 percent by weight of the solution, and also containing, as a wetting agent,a sulfonated fatty alcohol. The cleaned object is then washed thoroughlywith distilled water to remove all traces of the cleaning solution, andthen dried. I

After preliminary mechanical cleaning by whatever conventional methodmay be employed, the surface to be coated is then subjected to heattreatment to efiect removal of residual contaminants by distilling orburning these off the surface, such heat treatment resulting in an absoashort interval of time, to a gas flame from one or a series of burners,as illustrated at it in Fig. 3. For example, the rough or irregularlysurfaced article l5 may, if desired, be subjected to the flame from astandard Bunsen burner (about 1870 C.) to an oxy-hydrogen flame (about2800 C.); to oxy-acetylene flame (about 3500 C.) or

the like; or to the flame from a source of heat utilizing as acombustible constituent natural gas, illuminating gas, cracked petroleumhydrocarbons, or vaporized oil. In general I have found that anynon-smoky gas flame which may be secured by using sufflcient primary andsecondary air for complete combustion and which flame is also free ofash may be used for effecting the desired heat-cleaning treatment ofglass and other supports as hereinabove described, providing that duringcombustion the flame gives rise to a tem perature of at least 1000 C.

As is well-known, when glass articles and other siliceous articlesparticularly are suddenly heated, there is considerable danger offracture and spoilage occurring due to thermal strains set up within thematerial. Thus, when a glass support article is suddenly introduced intoa high temperature furnace, cracking occurs after the article has beenin such furnace for a relatively short time, and if the article isremoved from the furnace within shorter periods of time, it is foundthat the surface is not completely clean. By such means of heating, theheat is applied to the glass largely as radiant energy which isabsorbed, not only at the surface, but throughout the article, and therate of such heating is relatively slow due to the inefliciency ofabsorption of such radiant is conducted from such surface into theinterior I operation, final cleaning by heat may be effected or body ofthe glass article. In this way, the temperature of the surface of theglass may be raised to a sufliciently high temperature to burn off andto thoroughly clean the surface without effecting thermal shock orfracture within the article or support material, and when applying thegas flame the cleaning can thus be effected within very short periods oftime.

In a siimlar way, theuse of a gas flame applied to the surface forcleaning has been found desirable with regards to permitting rapidapplication or condensation of a protective organic liquid filmimmediately thereafter, since the gas flame does not introduce either toglass, siliceous, or metal supports or articles within the short time oftreatment of the flame, a suflicient amount of heat to raise the articleor support temperature to a very great degree. Thus, by the transfer ofheat from the hot surface into the interior of the article or supportbody, a considerable speed and degree of cooling is achieved after theflame is removed and the articles or supports quickly attain over-alltemperatures below 400 to 200 C., which will permit condensation of theliquids on such surfaces. Thus, the flame can immediately be followed bythe application of the organic liquid to the surface or surfaces of thearticle or support material, whereas a furnacetreated material wouldremain hot long periods and thereby increase the possibilities ofcontamination before the liquid protective film could be applied,

The application to the cleaned surface of the article l5, of the organicliquid in the form of vapor is illustrated generally at ill in Fig. 4 ofthe accompanying drawings, the resultant coated and,

protected article being seen at I5 in Fig. 5 and its protective coatingor covering layer or film at 20, as explained above.

In terms of continuous, automatic industrial by passing the chemicallycleaned articles on a conveyor,- or the like transmission system beforea battery of gas flames, so disposed that the areas to be cleaned andlater coated are swept by the flames, and at such a rate that thoroughc1eaning results.

One suitable apparatus for thoroughly cleaning the surfaces ofthearticles to be later coated, is shown in Figs. 6, 7, 8 and 9 of thedrawings, the

form shown in Fig. '7 differing from the apparatus.

a hood H is supported in any suitable manner. As shown, each of theseburners is supported above and adjacent one side of an endlesspowerdriven conveyer 22. Each of the burners is supplied with air portsand has a rectangular or oblong body portion having located in its innerwall or surface, a plurality of spaced nozzles or openings 2l a whichemit jets of flame l8a which, as clearly seen in Fig. 8 come intosurface contact with or impinge the outer surface or surfaces of thearticles l5 as they are moved by the conveyer between the spaced burners2|, Fuel is supplied to the burner bodies or housings through inletpipes or conduits 2 lb having control valves therein (not shown) whichare connected to a, suitable source of gas or other combustible mixturesupply (not shown). Each of the burners 2| is, as shown, supported byseveral strap-like brackets 2 I c which are attached to and carried bylongitudinal frame members of the apparatus. At opposite ends of thebody portions of the burners 2| there are located additional burners orburner units l2l. These, as shown, bridge the space above the articlesl5 and conveyer 22 and their jets of flame are preferably directedinwardly and downwardly toward the moving articles, as indicated by thearrows in Figs. 6 and 7. The end burner sections throw out flames which,with the flames i8a, en-

tirely blanket or envelop the surfaces of the articles l5. Thus,relatively flat articles, as well as the type shown, will be directlysubjected to the hot flames from the battery of burners. As clearly seenin Figs. 8 and 9, the gas jets or flames l 8a spread over the entirearea of the outer surfaces of each of the articles I5 so as to burn offand thus thoroughly cleanse these surfaces.

Since it is desirable that all surfaces of the articles be directlycontacted by the hot flames from the bumers, I have provided suitablemeans to cause the turning or revolving, no matter how little, of thearticles I5 a they are passed by the conveyer through the flame area. Asshown, see particularly Fig. 9, such means may be in the form of aslightly curved steel or other metal arm I22 having a series of idlerrollers l22a with which the articles l5 come in contact as they arepassed through the flame area by the conveyer 22. Such contact causesthe articles to shift or turn to present all surfaces thereof to theflames.

The conveyer 22 may be of any suitable type such, for example, as oneformed from a plurality of transversely extending metal slats, rods orbars which are supported or carried at their opposite end by suitableendless chains 22a. If desired, the conveyer belt, or the like, may beformed from heavy wire mesh h'aving relatively large openings, or arelatively heavy and fine mesh, such as used in glass machinery, may beemployed. The conveyer 22 is preferably supported at its opposite endsby sprockets 23 and 24 over which the endless chain 22a travel. As seenin Fig. 6, the conveyer may be power driven by a drive chain (not shown)which meshes with a gear or smaller sprocket 25 associated with thesprocket 24, from a suitable source of powe (not shown).

Protection of a thoroughly cleaned surf ce from contamination isassured, I have discovered as above set forth, by immediately depositingthereon after the flaming, and after the support article has partiallycooled, a fllm or layer of an organic liquid which is not particularlysubject to volatilization at the temperature of the partially cooledsurface, or at the temperature at which it is desired to protect thesurface during storage prior to its being coated with metal or othermaterial.

I have found that organic liquids of relatively high boiling point areeminently satisfactory for such purposes. Thus, organic liquids ofboiling point in the general range 200 to 400 C. as, for example,-methyl anthracene, -ethyl naphthalene, -naphthol, o-phenyl phenol,biphenyl, dibutyl phthalate, diethyl phthalate, dimethyl phthalates,diethylene glycol mineral oils, are all suitable for this purpose. It isto be distinctly understood, however, that I do not limit myself to theuse of pure organic liquids, or to single compounds only. As alreadydescribed, the function of the liquid film is to prevent contaminationof the cleaned surface. I have found that organic liquids boiling in thegeneral range 200 to 400' C. exhibit the necessary quality ofevaporating very slowly at ordinary temperatures, even when in the formof very thin liquid films. They may, therefore, serve verysatisfactorily as protective films for the purposes of this invention,permitting storage of the articles so coated until it is desired toundertake deposition operations. I have further found that these organicliquids are sumciently volatile under high vacua of the order of, forexample, 0.1 mm. to 10 to the minus 5 mm. of mercury, so that theyreadily evaporate. Alternatively, being organic liquids, they may bereadily removed from protected surfaces by electrical glow discharge andby direct oxidation of such films during such treatment. Any organicliquid, or mixture of organic liquids, serving this function, and ofsufficiently high boiling point to preclude substantial volatilizationand loss at the temperature at which the surface is to be pro tected,will, therefore, be found suitable for such application.

I have found that deposition of the protective liquid layer may bereadily accomplished by ex- 40 posing the surface to be coated at atemperature below the boiling point of the coating liquid, to the vaporsof the liquid at or around the boiling temperature. Condensation ofvapors on the surface of the article immediately occurs, with thedeposition of an extremely thin liquid film, covering the articlecompletely regardless of how irregular its surface may be. As a matterof mechanical expediency such operations may be readily effected byintroducing the article to which a protective coating is to be appliedinto a. chamber saturated with the vapor of protective liquid. Vapor maybe supplied in this way, for example, by boiling a supply of the liquidwithin the chamber itself, or by boiling in a reservoir from whicheffluent vapors are conducted into the chamber. In the latter event, itmay also be found desirable to preheat the gases prior to entering thechamber, and it is of course necessary to maintain temperatureconditions relating to the chamber at such' a'level that saturation ofthe atmosphere th'erein with vapors of the coating liquid is assured.

Deposition operations may also be suitably conducted by spraying theorganic liquid as a fine mist over the surfaces or articles to beprotected. Such a technique provides a relatively thick protectivecoating of liquid and is, therefore, preferable in certain instances todeposition by condensation. Obviously, too, relative simplicity ofequipment may render spraying operations more attractive, economically,for some applications than condensation. Such spray application may beconducted with a continuous belt under a hood, immediately followingflaming treatment upon such belt, preferably employing compressed nitro-2,883,470 gen or carbon dioxide asthe gas fed to the spray gun todisperse and spray the organic liquid.

To definitely provide protection of a completely cleaned surface, it isdesirable to subject the surface to liquid coating operationsas-hereinabove described as soon after conclusion of the final flamecleaning step as may be, since contamination by atmospheric vapors andlint, if from no other source, is otherwise unavoidable. Interms ofvautomatic, continuous operation, therefore, I find it desirable,immediately after the heat treatment, to conduct the thoroughly cleanedarticles into a vapor chamber, such as shown in Figs; 6 and '7. Since inflaming it is only necessary to apply the intense heat to the surfacesof the articles of glass, siliceous material, or metal, for a relativelyshort time, these articles cool quickly either by the heat beingconducted within the mass of such support articles, Or otherwise.

Consequently the vapors of the high-boiling protective liquid readilycondense on the articles shortly after flaming. The vapor chamber may,therefore, be of such length as to ensure that sufficient cooling of thearticle occurs to bring about vapor condensation upon its surface.

Referring further to Figs. 6, '7, 8 and 9 of the drawings, I shall nowdescribe that portion or unit of the two forms of apparatus shown inthese figures in which the temporary protective film or coating of asuitable organic liquid is applied to the thoroughly cleaned surfaces ofthe articles, such as the articles I 5, as they are fedby the conveyerbeyond the jets of flame |8a which have burned off all foreign matterfrom thesurfaces of the articles.

As shown in Fig. 6, the conveyer 22 extends through a chamber within theunit for applying the temporary protective film or coating. As seen inthis figure, a substantially rectangular housing 31 is provided. Thehousing is of doublewalledconstruction and the space between the wallsis preferably filled with some suitable insulating material, indicatedat 32. The front dual walls of the housing have a substantiallyarchshaped Opening 33 'anda similarly shaped opening 34 is provided inthe rear end dual walls of the structure. Depending from the top orceiling of the housing is a series of baflle walls or partitions 35which, as shown, terminate at their lower ends a substantial distanceabove the articles I5 and preferably only slightly above the archedopenings 33 and 34.

Below the upper flight of the conveyer 22- there is positioned a pan ortank 36 which is open at its top and which is adapted to contain theorganic liquid to be boiled off in the form of vapors to fill thechamber or compartment 30. A pipe or conduit 31 extends into the pan 36and is perforated at spaced points, at 31a, to admit into the pan eithercarbon dioxide or nitrogen, or other non-combustible gas, for example,which is bu bbled through the organic liquid. The organic liquid withinthe pan is caused to boil and give off vapors into the chamber 30 by theprovision of an electrical heating element or coil 31b locatedimmediately below the bottom of the pan or tank 35. Thus, by heating theorganic liquid and by bubbling an inert gas through the same, suppliedto the pan by the pipe 31, such liquidis caused to vaporize, with thevapors rising through the openings in the conveyer 22 and completelyfilling the compartment or chamber 30 to provide therewithin a mist-likeatmosphere of vaporized organic liquid. As the vapors-come into contactwith the relatively cooler surfaces of the articles,

they condense and form on said surfaces a continuous film or coating 20(Fig. 5) of the organic liquid for protecting the previously cleanedsurfaces of the articles. As the coated articles l5 emerge from thecompartment 30 through the discharge opening 34, they may be removedtherefrom and placed in storag In Fig. 7 of the drawings I have shown asomewhat modified vaporizing unit. As in the form of Fig. 6, a chamber30 is provided within a housing or casing of double-walled constructionshown as a whole at 3|. Openings 33 and 35 are provided at the front andrear end walls, respectively. Suitable insulation 32 is provided in thespace between the double walls of the housing and suitable electricalresistance or coils 32a are also located within the space between thewalls of the housing to permit heating these to prevent con densation.Suitable ballie walls 35 are also provided in the compartment or chamberof Fig. 7

in substantially the same manner as in Fig. 6.

In lieu of the vaporizing pan or tank 36 and the heating element 31b ofthe preceding form shown in Fig. 6, in the present form of my inventionthe organic liquid is preferably heated and vaporized outside the unitor apparatus and supplied to the chamber or compartment 30 in the formof vapor. For this purpose there is provided a vaporizing pot or boiler36aconnected bya tube or pipe 36b to a manifold 36c opening at spacedintervals 3611 into the chamber or compartment 30 through a wallthereof. The pipe 36b is preferably maintained in a heated condition byan electric resistance coil 36c which surrounds the pipe, the pipe beingfurther maintained in heated condition to maintain the vaporizedcondition of the organic liquid, by means of an insulating housing orcasing 36]. The pot 35a and the organic l quid therein are heated toboil the liquid by an electrical heating element or unit 369' which, as-

shown, preferably surrounds the base portion of the pot 36a.

A non-combustible gas is bubbled through the heated organic liquid bysupplying same through pipe 31 having openings or perforations below theliquid level. By thus feeding an inert non-combustible gas through theboiling organic liquid in the apparatus as shown in Figs. 6 and 7. acontinuous slight positive displacement of gas from the coating chamber30 is provided and a non-combustible mixture of vaporized organic liquidand inert gas is maintained in the chambers, thus avoiding anyaccidental igniting of such vapors by the adjacently located gas flames.

When the liquid within the pot 36a is heated and vaporized, the vaporstherefrom pass through the insulated and additionally heated tube orpipe 36b, manifold 36c and openings or ports 36d, into the chamber orcompartment 30 so as to provide within said chamber a mist-likecondition of the vapors. A the vapors strike the relatively coolersurfaces of the articles l5 passing through the chamber, they arecondensed and thus provide a protective film or coating of organicliquid upon the thoroughly. cleaned surfaces of the articles. As theprotected thoroughly cleaned articles l5 issue through thedischargeopening 34, they may be removed'to storage.

In both of the forms of Figs. 6 and 7 it will be noted that the frontand rear walls of the housing 3| and the baffles 35 are provided withdrain troughs 3la which serve to collect any of the surplus condensedvapors and direct them outside the chamber or compartment for re-use.

Upon removal from the chamber, the articles may be stored for as long aperiod as desired, without any danger of surface contamination.Alternatively, it may be desired to coat the protected surfacesimmediately with a metallic refiective coating, or a low-reflective orother type of coating.

In any case, when it is desired to undertake such coating or depositionoperations, the protective organic liquid film may be readily removed toexpose a thoroughly clean surface upon which metallic or other coatingdepositions may be successfully effected by known thermal evaporation orsputtering means. Thus the protective layer, along with foreign matterwhich may have settled upon its surface, may be removed by subjectingthe surface to heat, or preferably, to a vacuum and to an electricalglow discharge, in a vacuum of, say, about 0.01 millimeter. Theadvantages of effecting coating removal by evaporation of the organicliquid within a vacuum, with or without applying heat, or by electricalglow discharge methods are apparent. Thus, for example, both removal ofthe high-boiling liquid and deposition operations of metals or othermaterials may be conducted consecutively in the same vacuum chamber,thereby precluding the possibility of contaminating the cleaned surfaceprior to deposition.

Referring now particularly to Fig. 10 of the drawings, I have showntherein a suitable apparatus providing a chamber within which thetemporary or provisional surface protective coat ing may be removed froman article and to the surface or surfaces of said thoroughly cleanedarticle, a final and permanent coating, such as a reflective coating,may be applied by deposition resulting from thermal evaporation.

In Fig. 10 I have shown one form of apparatus which is adequately suitedto the purpose of performing the operations just referred to. As shown,the apparatus comprises a supporting base 38 upon which is mounted asuitable housing 39 provided with a semi-spherical or dome-like top andwith a surrounding base flange or projection 39a which has a tightsealing fit with the top surface of the base 38 to provide a sealedchamber or compartment 40 within the housing walls.

The chamber 40 is adapted to be completely evacuated of air and have ahigh vacuum created therein. For this purpose, evacuating means isprovided, such means being in the form of suitable pumps (not shown) forevacuating or withdrawing the air from within the chamber through anoutlet pipe 38a which latter is in communication with the chamber 40through the base 38.

When it is desired to provide upon the thoroughly cleaned andsurface-protected article I5, a final and permanent coating, such as amirrored or reflective surface coating, the article with its protectivecoating layer or film is placed upon a suitable support 38b which, ifdesired, may be caused torevolve or rotate in any suitable manner, as bymeans of an open-type greaseless electric motor M drivingly connected atD to the support 38b, said support being suitabl mounted upon the base38. While I have shown a single article l5 located within the chamber40, it will be understood that my invention contemplates placing withinthe chamber a plurality of articles which may be supported uponindividual supports or platforms which may or may not be caused torevolve. Moreover, a common supporting base or platform may be employedfor all of the articles; or they may be placed directly upon thesupporting base 38 of the apparatus.

After the article or articles l5 have been so positioned, the housing 39is placed in position upon the base and the chamber 40 is then evacuatedas desired by operating the pumps previously referred to. After a vacuumhas been created, the temporary protective film or layer 20 formed fromsome suitable organic liquid, starts to evaporate within the vacuum andis further removed by subjection to an electric glow discharge andbombardment from an electrode H by energizing said electrode to providean electric glow discharge within the vacuumized chamber. In the form ofapparatus shown, I use the wall of the chamber, if formed from metal, asone electrode, as shown at Ma. This operation removes the temporaryprotective film 20 from the article or articles and also removes anyforeign matter on said film by bombardment, by the boiling duringevaporation of the organic protective film and by oxidation. Ipreferably apply to the electrodes 4| and Ma a high tension electricalcurrent of 5,000 to 30,000 volts and about 3 k. v. a. of current.

Alternatively the protective organic liquid film may be removed byheating the article or articles l5 after positioning within the vacuumchamber 40, by energizing the heater wire or wires W and by evacuatingthe chamber. This causes a rapid ebullition of the liquid film whichcarries off with it any contaminations which may have fallen upon theprotective coating while the article was held in storage. The articlemay then be further glow discharged, if desired.

After the temporary protective coating or layer 20 has been completelyremoved and suitable vacuum conditions have been established, thefilament 43 of an evaporating unit 42 and to which suitable material tobe evaporated has been applied in any suitable manner, is electricallyenergized to effect the thermal evaporation of said material and applyit to the freshly exposed clean surface or surfaces of the article orarticles l5 by deposition resulting from the thermal evaporation of thematerial on the filament 43. Because of the fact that the surface whichhas just been coated by deposition was thoroughly cleaned, protectivelymaintained in such condition, and only exposed in such cleaned conditionwithin the vacuum chamber, before the deposition of the material, thefinal coating, layer or film will be of a permanent nature and adherefirmly to the surface of the article without the danger of becomingloose and rubbed off or removed therefrom during use.

While I have described and illustrated the use of my method or processand apparatus for carrying it out in connection with articles such asvases or the like, various other articles formed from various materialsand of varied sizes and shapes which are eventually to be provided witha final metallized or other protective coating, can be treated inaccordance with my present invention. For example, if it is desired tocoat iron bolts, or the like,with a coating of cadmium, for example, theordinary bolts taken from stock with dirty surfaces, may be vapordegreased and then placed on the conveyer 22 and subjected to the fiametreatment in much the same manner as are the articles l5 disclosed inFigs. 3, 6, '7, 8 and 9 of the drawings. After the flame treatment ofthe bolts, they are passed through the vaporizing chamber 30 of theapparatus of either Fig. 6 or 7 and removed therefrom with their2,388,470 protectivesurface coating to storage. If desired,

however, they may be carried directly from the preliminaryprotectivecoating chamber 3| into a furnace, such as the electricfurnace shown asa whole at 50 in Fig. 11. The furnace II, as shown, isprovided with a double-walled casing having insulation "between thewalls and an electric heating element 83 which is also located betweenthe walls. I

Upon the furnace base or floor 54 there is preferably located an opentop pot or crucible 5| whichcontains the metal or other material to betrogen or carbon dioxide, may be introduced into the furnace so as tomaintain the furnace under a slight positive pressure.

Because of the high heat within the furnace the organic liquidprotective film or coating on the bolts is immediately evaporated so asto ensure the removal therefrom, not onlyof the protective coating butalso of any foreign contaminants. Since the atmosphere within thefurnace 60 is saturated with cadmium vapors, the bolts rapidly becomecovered with the desired finish layer or coating of cadmium. Afterremoving from the furnace the bolts havea uniform, adherent cadmiumcoating and excellent corrosionresistance properties.

While I have described one type of: furnace, such-as that shown at 50 inFig. 11, it will be understood that the surface-protected bolts may havea final coating applied" thereto in any other suitable type of furnace,or by any other suitable means. Moreover, any desired type of conveyermay be employed for moving the bolts through the furnace. The conveyer58 is preferably provided with a plurality of pointed humps or bumps 56aso that the bolts B will not lie fiat on the conveyer. The upper fiightof the conveyer is preferably supported by longitudinal bars or rails,one such being shown at 51. 'As shown, the rail 51 is spring-supportedat its front end by a bracket, rod and spring assembly, shown as a'wholeat 58. A It might be For this purpose, as shown, thebar 51' is supportedat its rear end by'a bracket or arm 59 carrying ,a spring-cushioned rodor pin 60 at-, tached to the bar. The under face-of the bar, adjacentpin 60, is provided with an idler roller 6| which is in engagement witha rotatable notched roller or wheel 62 carried by the inner endportionof the bracket or arm 58. A drive or sprocket chain 63 serves to rotatethe roller or wheel 62 at'high speed. The'chain is driven desirable tovibrate the conveyer.

tribution-of the cadmium or other final or finish coating.

"Il'hefollowing examples will illustrate certain applications of myinvention. It is to hammerstood, however, that I intend these asillustrative only, and not limiting. They should be interpreted,therefore, in an illustrative rather than in a limiting sense.

Example 1 A common glass tumbler, vase, or the like, such as that shownat I I in Fig. 1 and a section of sheet glass (not shown) wereseparately subjected to a preliminary mechanical cleaning to removesuperficial contaminants. The articles were washed with a chemicalcleaning solution consisting of trisodium phosphate, precipitated chalk,and, as a wetting agent, a sulfonated fatty alcohol. After reasonablythorough washing, the cleaned articles were rinsed thoroughly withdistilled water to remove all traces of the cleanin solution. One sucharticle is shown at it in Fig.

2, the remaining particles of dirt being seen at IT.-

The preliminarily or partially cleaned surfaces of the articles, such asthe article liupon which a-metallic film was subsequently to bedeposited, werethen completely cleaned from contaminants by passlng'thearticles before a battery of Bunsen burners fed with illuminating gas,so disposed that all those surfaces were momentarily but completelyswept by the flames for a period of about 60 seconds or less. See, forexample, the burners 2| and III of Figs. 6,7, Band 9. v I

Immediately after this heat treatment the articles were passed into achamber, such as the chamber of Figs. 6, 7 and 8 and therein-saturatedwith vapors (see vapors illustrated at IS in Fig. i) of'diethyleneglycol. Although the heat treated surfaceshad been subjected to a flametemperature of approximately 1870 C., and although only as shorta periodof time'as possible had elapsed since the heat treatment, the surfaceshad nevertheless cooled sufiiciently so that their temperature was wellbelow the temperature of the diethylene glycol vapors (approximately 245C.) and condensation of diethylene glycol on the surfaces of thearticles at once occurred, resulting ina film (see film or coating 20,Fig. 5) of the compound completely covering the articles. The

protected articles, such as shown inlFig. 5, were then stored.

After several days had elapsed, it being desired to undertake suitablemetallic deposition operations. the articles were removed from storageand placed in a conventional. v'acuumized chamber where such'operationswere to be conducted, one such chamber being shown at 40 in Fig. 10 ofthe accompanying drawings. The pressure in the chamber was reduced toapproximately 0.08 mm. of mercury. The protective film 20 of diethyleneglycol began immediately to evaporate rapidly. Evaporation wassufllciently rapid, in fact, to ensure physical removal by blowing offof any foreign contaminants which might have become from any suitablesource of power (not. shown).

Thus, the bar 5! and also the conveyer will be caused to bounce orjiggle up and down against the action of spring 60a to cause agitationormovement of the bolts B so that all surfaces the crucible or pot 5|.

dergoing treatment, such maybe vibrated in suit-. able manner to ensurethe even and complete dislodged on the protective film 20. By reducingthe pressure within chamber to about 0.02 to 0.01

1 mm. of mercury, and by electrically actuating with a high voltage suchas 15,000 volts, the electrode or electrodes with which the vacuumizedchamber was equipped, see, for example, electrode 4| in Fig. 10, a glowdischarge resulted which, by

oxidation and by bombardment, effected complete removal of theprotective films.

It is to be understood that the combination of vacuum and electric glowdischarge was not necessary to effect complete removal of the protectivefllms, since either of these measures, separately, would have ensuredsuch complete removal.

In some trials upon samples removed from the vacuumized chamber at thispoint, the cleaned surfaces were demonstrated to have been completelyfreed from contaminants by exhibiting black-colored breath figures andby causing flne, clean glass fibers to seize and rasp when drawn acrossthe cleaned surfaces, both of which tests, as hereinabove set forth aresatisfied only by glass surfaces of absolute cleanliness and freedomfrom contaminants.

The exposed, completely uncontaminated surfaces were then subjected,without removal from the vacuumized chamber ll, to depositionoperations, performed by the thermal evaporating unit A glass lens and aprism which it was desired to coat with low reflection films ofmagnesium fluoride, were preliminarily mechanically cleaned by athorough scrubbing with a brush having an application of a chemicalcleaning solution consisting of trisodium phosphate, calcium carbonate,and a sulfonated fatty alcohol as melting agent. After washingoperations were completed, the articles were rinsed with distilled waterto remove all traces of the cleaning solution. The articles were thenconveyed past a battery of oxy-acetylene flames so disposed that thesurfaces of the articles were momentarily but completely swept by theflames therefrom, see, for example, the burners 2i and iii of Fig 6, 'l,8 and 9. Immediately after this heat treatment, the prism and the lenswere introduced into a chamber, such as chamber of Figs. 6. '7 and 8,and saturated therein with vapors of dibutyl phthalate.

Again, as in Example 1, although the surfaces of the articles had beenexposed to a high temperature, in this case approximately 3500 C., theextremely short interval of time between this heat treatment fromburners 2i and the introduction of the articles into the condensationchamber 3|, had nevertheless been ample to permit cooling of the flamedsurfaces to a temperature below that of the dibutyl phthalatevaporsapproximately 340 C, As in Example 1, condensa- Lion of organicliquid vapors completely covering the cleaned articles at once occurred.

The thus protected articles were then stored for several days, until itwas desired to undertake coating deposition operations. At that time thearticles were remved from storage and placed in the conventional vacuumchamber 40 designed for such operations. The protective dibutylphthalate films, together with foreign contaminants which might havelodged thereon during storage of the articles, were then removed, asdescribed in Example 1, within the vacuum chamber 40 by evaporation andelectrical glow discharge, as from electrode 4|, Fig. 9. If the glasssupport is to be heated during deposition of the low reflective film orcoating, the heating of the glass within the vacuum prior to depositionof the magnesium fluoride or other material, may sumce to removecompletely the organic liquid film, such as the film 20 of Fig. 5.

Immediately upon conclusion of the operations of removing the protectivefilm and while remaining in chamber 40, the surfaces of the articleswere coated with a thin film of magnesium fluoride by conventionalthermal evaporation means employed in depositing such low-reflectioncoatings, such as by means of the thermal evaporating unit 42, Fig. 10.The low reflection films were without flaw or blemish spots, exhibitedgood adherence to the surfaces on which they were deposited, and, inintensive service tests, proved entirely satisfactory, demonstratingexcellent performance characteristics.

Example 3 A number of steel bolts, such, for example, as those seen inFigs. 11 and 12, on which it was intended to deposit a thin layer ofcadmium. were subjected to a preliminary mechanical cleaning by tumblingin a mixture of sawdust and whiting. Alternatively, they may be cleanedin a well known manner in a solvent-vapor degreaser. After cleaning thebolts reasonably thoroughly in this manner, they were removed from thetumbling barrel (not shown) and adherent cleaning mixture removed byblowing with clean, dry compressed air. The bolts were then completelycleaned of contaminants by conveying them past a battery of natural gasburners (not shown) so disposed that all surfaces of the bolts weremomentarily but completely swept by the flames from the burners.

Immediately after passing the flames, the bolts were sprayed (employingcompressed nitrogent in the spray gun) with mineral oil with suchthoroughness that the entire surface of each bolt was subjected to thefine, mist-like spray. The mineral oil, upon contact with the bolts,covered all surfaces completely with a protective liquid layeror film.The protected bolts were then stored until it was desired to undertakemetallic deposition operations. After a period of ten days the boltswere removed from storage and introduced into a furnace, such as thefurnace 50 of Fig. 11, at atmospheric pressure, the temperature of whichwas in excess of about 770 C. The furnace 50 was equipped with a vesselor crucible 5| containing boiling cadmium, in consequence of which theatmosphere of the furnace was saturated with cadmium vapors. The vessel5| was heated in any convenient and suitable manner, as 'by electricalresistance 52, located below the pot or vessel. The protective mineraloil coating on the bolts evaporated immediately from the bolts with suchrapidity as to ensure physical removal of any foreign contaminants whichmight have become lodged thereon. The thoroughly cleaned bolts becamecovered with the desired layer of cadmium.

After removal from the furnace 50 the finishe :1

- bolts exhibited a uniform, adherent cadmium coating and good corrosionresistance properties.

In Fig. 13 of the drawings I have illustrated, schematically, thearrangement or order of the various parts or units which togetherconstitute the apparatus of the present invention and which units orelements of the whole may be employed for performing or carrying out theseveral steps of my method or process. In this figure, the circle Crepresents conventional apparatus or equipment for mechanically orchemically preliminarily cleaning the surfaces of articles, such as thearticles 15 of the preceding views. The circle designated F representsthe flame treating unit or equipment for flame-treating thepreliminarily cleaned articles l5.

The circle designated PC is intended to represent that portion or unitof the apparatus where the temporary protective coating of an organicliquid is applied tothe thoroughly cleansed surfaces of the articles l;and the circle designated FC is intended to represent that portion orunit of the apparatus by the use of which the temporary protectivecoating is removed from the articles and the final or permanent coating,which may be of a reflective nature, is deposited upon the thoroughlycleaned surfaces of the articles.

As set forth fully above the articles are first preliminarily cleanedmechanically or chemically in the unit or at the station C. They arenext completely freed of all contaminants by the flame treatment at unitor station F. The thoroughly cleansed surfaces are then provided with atemporary protective organic liquid coating at unit or station PC. Ifdesired, the temporarily surface-protected articles may be placed instorage or, if desired, they may be immediately placedin the unit or atthe station FC where the temporary protective coating and anyaccumulation of contaminants thereon are removed to reveal thethoroughly cleansed surfaces of the articles, whereupon and in the sameunit or at the same station, FC, the final and permanent coating isdeposited upon the cleaned surfaces.

Widely diverse embodiments of my invention may obviously be made withoutdeparting from the spirit and scope thereof.

Having thus described my invention, what I claim is:

1. The method of coating a surface of a noncombustible supportmaterialby thermal evaporation within a vacuum chamber, comprising thesteps of subjecting the support material to a preliminary mechanicalcleaning, momentarily subjecting the support material surface directlyto a gas flame of a temperature of over 1000 C. to remove contaminantstherefrom, immediately thereafter applying to the surface bycondensation of a vaporized liquid a removable liquid protective filmcovering of a high boiling inert organic liquid having a boiling rangeof the order of 200 to 400 C. to the cleaned support surface,

placing the thus protected support material in a highly vacuumizedchamber, removing said liquid protective film by a forced evaporationwithin the chamber, and thereafter applying a coating by thermalevaporation to the freshly exposed cleaned surface while remaining insaid vacuum chamber.

2. A method according to claim 1, wherein the coating is a mirrorreflective coating.

3. A method according to claim 1, wherein the support material is glass.

4. A method according to claim 1, wherein the support material is glassand wherein the coating is a low reflection coating applied by thermalporarily protecting the cleaned surfaces thereof against furthercontamination, comprising means for subjecting the surfaces of the glassto contact briefly with a hot flame from a burner to remove contaminantstherefrom, and means for applying by condensation of vapors a removableprotective liquid surface coating to the glass to prevent contaminationof the clean surfaces thereof.

7. Apparatus for cleaning support material and for protecting thecleaned surfaces thereof against further contamination, comprising meansfor sub-- jecting the surfaces of the support material to contactbriefly with a hot flame from a burner to completely remove anycontaminants therefrom, adjacent means for applying a protective liquidsurface coating to the support material by condensation of the vaporizedliquid, said adjacent means comprising a chamber saturated with thevaporized liquid, and means for supplying the vapors of the liquid.

' 8. Apparatus for cleaning support material and for protecting thecleaned surfaces thereof against further contamination, comprising meansfor subjecting the surfaces of the support material to contact brieflywith a hot flame from a burner to completely remove any contaminantstherefrom, adjacent means for applying a protective liquid surfacecoating to the support material by condensation of the vaporized liquid,said adjacent means comprising a chamber saturated with the vaporizedliquid, means for supplying the vapors of the liquid, and means forprogressing the support material past the burner and through saidvapor-filled chamber.

9. Apparatus for cleaning support material and for protecting thecleaned surfaces thereof against further contamination, comprising meansfor subjecting the surfaces of the support material to contact brieflywith a hot flame from a burner to completely remove any contaminantstherefrom, adjacent means for applying a protective liquid surfacecoating to the support material by condensation of the vaporized liquid,said adjacent means comprising a chamber saturated with the vaporizedliquid, means for generating the vapors of the liquid, means forsupplying a noncombustible gas to admix with said vapors within thegenerating means, and means for conducting the mixture ofnon-combustible gas and vapors of the liquid from the generating meansto said chamber.

10. Apparatus for cleaning support material and for protecting thecleaned surfaces thereof against further contamination, comprising meansfor subjecting the surfaces of the support material to contact brieflywith a hot flame from a burner to completely remove any contaminantstherefrom, adjacent means for applying a protective liquid surfacecoating to the support material by condensation of a vaporized liquid,said adjacent means comprising a chamber saturated with the vaporizedliquid, means for generating the vapors of the liquid, means forsupplying a non-combustible gas to admix with said vapors within thegenerating means, means for conducting a mixture of the non-combustiblegas and the vapors of the liquid from the generating means to thechamber, and means for progressing the support material past the burnerand through said vapor and gas-miXture-fllled chamber,

WILLARD L, MORGAN.

